Arsenic is a ubiquitous and carcinogenic element found in various species in the terrestrial aquatic environment, coming from both of natural geogenic and anthropogenic sources. During the past decades, numerous reports have documented that residents being exposed to excessive levels of arsenic through drinking water and food chain, may result in serious public health concern. Arsenic and its compounds are highly mobile in the ecosystem, being biological available to organisms and producing toxicities, which are, to a large extent, dependent on arsenic speciation and oxidizing state. It is thus imperative to identify and clarify the arsenic behaviors in the environment. This review summarizes the process and mechanism of arsenic transformation and transportation in waters, particularly at the sedimentwater interface. In addition, various factors that affect the retention and release of arsenic, such as Eh-pH, metalloid oxides, organic matter, clay minerals and microbial activities, are also presented with examples.